diff --git a/lib/fluent/config/types.rb b/lib/fluent/config/types.rb
index 66ef37ad39..0ff2c2c475 100644
--- a/lib/fluent/config/types.rb
+++ b/lib/fluent/config/types.rb
@@ -20,6 +20,10 @@
 
 module Fluent
   module Config
+    def self.reformatted_value(type, val, opts = {}, name = nil)
+      REFORMAT_VALUE.call(type, val, opts, name)
+    end
+
     def self.size_value(str, opts = {}, name = nil)
       return nil if str.nil?
 
@@ -104,6 +108,16 @@ def self.string_value(val, opts = {}, name = nil)
       Config.string_value(val, opts, name)
     }
 
+    def self.symbol_value(val, opts = {}, name = nil)
+      return nil if val.nil?
+
+      val[0] == ":" ? val[1..-1].to_sym : val.to_sym
+    end
+
+    SYMBOL_TYPE = Proc.new { |val, opts = {}, name = nil|
+      Config.symbol_value(val, opts, name)
+    }
+
     def self.enum_value(val, opts = {}, name = nil)
       return nil if val.nil?
 
@@ -130,7 +144,13 @@ def self.enum_value(val, opts = {}, name = nil)
           raise ConfigError, "#{name}: #{e.message}"
         end
       else
-        val.to_i
+        i = val.to_i
+        # string will convert to 0, return nil if not actually "0"
+        if i == 0 && val != "0"
+          nil
+        else
+          i
+        end
       end
     }
 
@@ -176,6 +196,7 @@ def self.enum_value(val, opts = {}, name = nil)
         when :bool then Config.bool_value(value, opts, name)
         when :time then Config.time_value(value, opts, name)
         when :regexp then Config.regexp_value(value, opts, name)
+        when :symbol then SYMBOL_TYPE.call(value, opts, name)
         else
           raise "unknown type in REFORMAT: #{type}"
         end
diff --git a/lib/fluent/env.rb b/lib/fluent/env.rb
index 2b0bf5c8d7..7ac5e02f5e 100644
--- a/lib/fluent/env.rb
+++ b/lib/fluent/env.rb
@@ -15,13 +15,14 @@
 #
 
 require 'serverengine/utils'
+require 'fluent/env_utils'
 
 module Fluent
   DEFAULT_CONFIG_PATH = ENV['FLUENT_CONF'] || '/etc/fluent/fluent.conf'
   DEFAULT_PLUGIN_DIR = ENV['FLUENT_PLUGIN'] || '/etc/fluent/plugin'
   DEFAULT_SOCKET_PATH = ENV['FLUENT_SOCKET'] || '/var/run/fluent/fluent.sock'
   DEFAULT_BACKUP_DIR = ENV['FLUENT_BACKUP_DIR'] || '/tmp/fluent'
-  DEFAULT_OJ_OPTIONS = {bigdecimal_load: :float, mode: :compat, use_to_json: true}
+  DEFAULT_OJ_OPTIONS = Fluent::EnvUtils::OjOptions.new.get_options
   DEFAULT_DIR_PERMISSION = 0755
   DEFAULT_FILE_PERMISSION = 0644
 
diff --git a/lib/fluent/env_utils.rb b/lib/fluent/env_utils.rb
new file mode 100644
index 0000000000..bd605db4c5
--- /dev/null
+++ b/lib/fluent/env_utils.rb
@@ -0,0 +1,50 @@
+require 'fluent/config'
+
+module Fluent
+  module EnvUtils
+    def self.convert_env_var_to_type(value, type)
+      Fluent::Config.reformatted_value(type, value)
+    end
+
+    class OjOptions
+      OJ_OPTIONS = {
+        'bigdecimal_load': :symbol,
+        'max_nesting': :integer,
+        'mode': :symbol,
+        'use_to_json': :bool
+      }
+  
+      OJ_OPTIONS_ALLOWED_VALUES = {
+        'bigdecimal_load': %i[bigdecimal float auto],
+        'mode': %i[strict null concat json rails object custom]
+      }
+  
+      OJ_OPTIONS_DEFAULTS = {
+        'bigdecimal_load': :float,
+        'mode': :concat,
+        'use_to_json': true
+      }
+
+      def initialize
+        @options = {}
+        OJ_OPTIONS_DEFAULTS.each { |key, value| @options[key] = value }
+      end
+
+      def get_options
+        OJ_OPTIONS.each do |key, type|
+          env_value = ENV["FLUENT_OJ_OPTION_#{key.upcase}"]
+          next if env_value.nil?
+
+          cast_value = Fluent::EnvUtils.convert_env_var_to_type(env_value, OJ_OPTIONS[key])
+          next if cast_value.nil?
+
+          next if OJ_OPTIONS_ALLOWED_VALUES[key] && !OJ_OPTIONS_ALLOWED_VALUES[key].include?(cast_value)
+
+          @options[key.to_sym] = cast_value
+        end
+
+        @options
+      end
+    end
+  end
+end
diff --git a/test/test_env_utils.rb b/test/test_env_utils.rb
new file mode 100644
index 0000000000..c6ee35c15c
--- /dev/null
+++ b/test/test_env_utils.rb
@@ -0,0 +1,41 @@
+require_relative 'helper'
+require 'fluent/test'
+require 'fluent/env_utils'
+
+class EnvUtilsTest < ::Test::Unit::TestCase
+  setup do
+    @oj = Fluent::EnvUtils::OjOptions.new
+  end
+
+  sub_test_case "module methods" do
+    test "convert_env_var_to_type" do
+      assert_equal :conor, Fluent::EnvUtils.convert_env_var_to_type("conor", :symbol)
+      assert_equal 8933, Fluent::EnvUtils.convert_env_var_to_type("8933", :integer)
+      assert_equal nil, Fluent::EnvUtils.convert_env_var_to_type("conor", :integer)
+      assert_equal true, Fluent::EnvUtils.convert_env_var_to_type("true", :bool)
+      assert_equal nil, Fluent::EnvUtils.convert_env_var_to_type("conor", :bool)
+    end
+  end
+
+  sub_test_case "OjOptions" do
+    test "when no env vars set, returns default options" do
+      ENV.clear
+      assert_equal Fluent::EnvUtils::OjOptions::OJ_OPTIONS_DEFAULTS, @oj.get_options
+    end
+
+    test "valid env var passed with valid value, default is overridden" do
+      ENV["FLUENT_OJ_OPTION_BIGDECIMAL_LOAD"] = ":bigdecimal"
+      assert_equal :bigdecimal, @oj.get_options[:bigdecimal_load]
+    end
+
+    test "valid env var passed with invalid value, default is not overriden" do
+      ENV["FLUENT_OJ_OPTION_BIGDECIMAL_LOAD"] = ":conor"
+      assert_equal :float, @oj.get_options[:bigdecimal_load]
+    end
+
+    test "invalid env var passed, nothing done with it" do
+      ENV["FLUENT_OJ_OPTION_CONOR"] = ":conor"
+      assert_equal nil, @oj.get_options[:conor]
+    end
+  end
+end
\ No newline at end of file